Comparative analysis of DLC and TiSiCN hard coatings against wear and corrosion

Service life of machine parts used in the oil and gas industry can be expanded by using coatings that improve surface properties such as wear and corrosion resistance. DLC coatings are known for their low friction coefficient, high wear resistance and chemical inertness. TiSiCN films are hard ceramics, so they provide good resistance to abrasive and erosive wear. In this work, these two coatings deposited on alloy steel AISI 4140 are comparatively analyzed. Thickness was measured and the coatings were characterized by XPS, DRX and Raman spectroscopy. Pin-on-disk adhesive wear and abrasive wear tests (ASTM G65) were carried out. Adhesion was evaluated by scratch test. Corrosion resistance was evaluated by salt spray test and potentiodynamic tests. DLC coatings presented low friction coefficient μ ~ 0,2, and a volume loss twice as low as TiSiCN, whereas the latter presented 30 times the abrasive wear resistance. The adhesion of TiSiCN was also superior. DLC showed higher corrosion resistance. (author)